1. Technical Field
The present invention relates to a liquid ejecting head such as an ink jet type recording head, and a liquid ejecting apparatus including the same, and in particular, a liquid ejecting head and a liquid ejecting apparatus ejecting liquid from a nozzle by displacing an island unit of a diaphragm unit partitioning a part of a pressure chamber, using a piezoelectric vibrator.
2. Related Art
A liquid ejecting apparatus includes a liquid ejecting head which is capable of ejecting liquid as droplets, and is an apparatus which ejects various kinds of liquids from the liquid ejecting head. As a representative apparatus of the liquid ejecting apparatus, for example, an image recording apparatus can be exemplified such as an ink jet type recording apparatus (printer) that includes an ink jet type recording head (hereinafter, referred to as a recording head), and ejects liquid ink as ink droplets from the recording head and performs recording. In recent years, liquid ejecting apparatuses are also applied to various kinds of manufacturing apparatuses such as a display manufacturing apparatus without being limited to the image recording apparatus.
As the ink jet type printer (hereinafter, simply referred to as the printer) which is a kind of liquid ejecting apparatus, there is a printer having a configuration which fluctuates the volume of a pressure chamber by displacing a diaphragm unit partitioning a part (opening surface) of the pressure chamber, using a piezoelectric vibrator to generate pressure fluctuation in the ink inside the pressure chamber and ejecting the ink from a nozzle (for example, refer to JP-A-07-195689).
The diaphragm unit includes a flexible film which seals the opening surface of the pressure chamber, and an island unit which is provided on this flexible film. This island unit is generally made of a rigid body such as a metal or the like formed in an approximately rectangular parallelepiped shape, and is a part which is joined to the tip of the piezoelectric vibrator. The flexible film around the island unit functions as an elastic film unit. When the piezoelectric vibrator is displaced in an expandable manner, the island unit is displaced towards the side away from the pressure chamber, or the island unit is displaced towards the side close to the inside of the pressure chamber, and accordingly the volume of the pressure chamber is fluctuated. It is configured that the pressure fluctuation of the ink in the pressure chamber is generated by the volume fluctuation of the pressure chamber, and the ink is ejected from the nozzle using this pressure fluctuation. Since the displacement of the piezoelectric vibrator is extremely small (for example, several tens of nm), it is preferable that the displacement of the piezoelectric vibrator be efficiently converted to the volume fluctuation of the pressure chamber.
In recent years, a plurality of nozzles are arranged with a high density in various printers to respond to the image quality improvement of the recording image. Accordingly, the pressure chambers which communicate with each of the nozzles are also formed with a high density. As a result, the dimensions of the piezoelectric vibrator, particularly the dimension in the nozzle array direction, tend to be small so that the rigidity of the piezoelectric vibrator is degraded. A piezoelectric vibrator with low rigidity tends to be deformed by receiving a reaction force when the island unit is displaced, and thus a failure in ejecting the ink may occur. Specifically, if the piezoelectric vibrator is easily deformed, the volume fluctuation of the pressure chamber is not sufficiently performed, and ejection properties (ink amount, flying speed or the like) of the ink ejected from the nozzles may fluctuate. Further, if the piezoelectric vibrator is easily deformed, an increase of the compliance (the degree of tendency to be deformed or softness per unit area) may occur by the same amount. If the compliance is increased, it is concerned that the meniscus vibration may be increased after ejecting the ink, and this vibration may exert a negative influence on the ejection properties.
Such problems exist not only in the ink jet type recording apparatus to which the ink jet type recording head ejecting the ink droplet is mounted, but also in liquid ejecting apparatuses to which other liquid ejecting heads ejecting liquid droplets other than ink are mounted.